U.S. Pat. No. 3,114,756 issued Dec. 17, 1963, discloses the composition of tetracyano-1,4-hydroquinone, a process for its preparation, the composition of tetracyano-1,4-benzoquinone and a process for its preparation from tetracyano, 1,4-hydroquinone. The process leading to tetracyano-1,4-hydroquinone originates from 2,5-dicyano-3,6-dihalogeno-1,4-benzoquinones. It is stated that it is not possible to introduce further cyano groups into 2,3-dicyano-5,6-dihalogeno-1,4-benzoquinones or 2,3-dicyano-5,6-dihalogeno-1,4-hydroquinones. Since 2,3-dicyano-5,6-dichloro-1,4-hydroquinone is the product of the reaction of chloranil (tetrachloro-1,4-benzoquinone) with potassium cyanide, it is implied that chloranil would not be a suitable starting material for tetracyano-1,4-hydroquinone. The process for the conversion of tetracyano-1,4-hydroquinone to tetracyano-1,4-benzoquinone utilizes as reagent "nitrous gases." These same chemical conversions are discussed at length by K. Wallenfels et al., Tetrahedron, 21, 2239-2256 (1965) and Angew. Chem. 73, 142 (1961).
E. A. Braude et al., Journal of the Chemical Society (London) 1954, p 3572 disclose that attempts to replace the chlorine atoms in chloranil with cyanide groups from cuprous cyanide were unsuccessful.
L. Bucsis et al., Chemische Berichte, 109, 2462-2468 (1976) disclose the isolation of tetracyano-1,4-hydroquinone in 5% yield as a by-product in the preparation of 2,3-dichloro-5,6-dicyano-1,4-hydroquinone from the reaction of chloranil with potassium cyanide. It is stated that, despite the low yields, this route to tetracyano-1,4-hydroquinone is preferred over the route of Wallenfels et al. due to shorter cycle time and availability of starting materials. There is neither disclosure nor suggestion of how to convert this low-yield process to a high-yield reproducible process.
O. W. Webster et al., J. Org. Chem, 30, 3250 (1965), disclose the preparation of tetracyano-1,4-hydroquinone from tetracyano-p-phenylendiamine via the bis(diazonium) compound in 35% yield. The tetracyano-p-phenylenediamine starting material was itself prepared in 3.7% yield from tetracyanoethane.
Thus, there exists no easily operable, reasonable yield route to tetracyano-1,4-hydroquinone. Nor is there a known process for the conversion of tetracyano-1,4-hydroquinone to tetracyano-1,4-benzoquinone that involves the use of stable, readily available reagents.
It is therefore an object of the present invention to provide a process for the preparation of tetracyano-1,4-hydroquinone.
It is a further object of the present invention to provide processes for the preparation of tetracyano-1,4-benzoquinone.
It is a further object of the present invention to provide novel electron-transfer complexes of tetracyano-1,4-benzoquinone.